Intrauterine growth retardation (IUGR) remains a major cause of intrauterine and neonatal death and is associated with a high morbidity in the neonatal period and potentially with morbidity extending to adult life. It is frequently associated with abnormalities of placental growth and/or function. IUGR can be diagnosed with standard obstetrical techniques such as ultrasonography. However treatment of IUGR remains inadequate and restricted to either maternal bedrest or premature elective caesarean section.
Immaturity of lung growth and development in fetal life may occur associated with IUGR or independent of it. Isolated failure of fetal lung growth is known as pulmonary hypoplasia and is a significant cause of neonatal death. It may be diagnosed prenatally. In prematurely born infants, immaturity of lung structure and function leads to the respiratory distress syndrome (RDS). RDS is currently treated by ventilation and pulmonary insufflation of surfactant but remains a major problem in neonatal nurseries. It has been the practice for many years to treat women at risk of premature birth or in premature labour, where delivery is delayed pharmaceutically, with steroid hormones which cross the placenta and mature the lungs. However this therapy only partially alleviates RDS.
It is known to those versed in the art that fetal growth is regulated in part by a hormone termed insulin-like growth factor-1 (IGF-1) which circulates in the fetal circulation and which has been demonstrated in a variety of animal models to regulate fetal growth and confirming clinical data are available. IGF-1 is made by fetal tissues. It however does not cross the placenta from mother to fetus. Therefore maternal administration does not directly affect fetal circulating levels of IGF-1 and that maternal administration of IGF-1 affects fetal growth indirectly (Liu L, Harding J E, Evans P C, Gluckman P D. "Maternal IGF-1 alters feto-placental carbohydrate and protein metabolism in pregnant sheep". Endocrinology 135 895-900; 1994). IGF-1 in the fetal circulation is derived from fetal tissues in particular from the fetal liver.
It is also known that the fetus swallows amniotic fluid.